We Keep Coding

How do you parse a nested JSON file like below using Processing JSON object?

How do you parse a nested JSON file like below using Processing JSON object? I am trying to figure out how to parse JSON that is multi-level.
{
"info": {
"description": "COCO 2014 Dataset",
"url": "http://cocodataset.org",
"version": "1.0",
"year": 2014,
"contributor": "COCO Consortium",
"date_created": "2017/09/01"
},
"images": [
{
"license": 5,
"file_name": "COCO_train2014_000000057870.jpg",
"coco_url": "http://images.cocodataset.org/train2014/COCO_train2014_000000057870.jpg",
"height": 480,
"width": 640,
"date_captured": "2013-11-14 16:28:13",
"flickr_url": "http://farm4.staticflickr.com/3153/2970773875_164f0c0b83_z.jpg",
"id": 57870
},

Have a look at JSONObject and JSONArray to see the available methods bellow on each page, each with documentation and examples.
Regarding your structure, here's a quick snippet on how you might access nested JSON objects and arrays:
// assume data is a JSONObject pointing to the loaded json data (via loadJSONObject / JSONObject.parse(), etc.
// access the info object
JSONObject info = data.getJSONObject("info");
// access the images array object
JSONArray images = data.getJSONArray("images");
// access a string inside an object
println(info.getString("description"));
// access a JSON object inside a JSON array
JSONObject firstImage = images.getJSONObject(0);
// acess an integer
println(firstImage.getInt("id"));
// ... and a string again
println(firstImage.getString("flickr_url"));
If you name your loaded JSONObject variable data, paste the the snippet above and run, it should print:
COCO 2014 Dataset
57870
http://farm4.staticflickr.com/3153/2970773875_164f0c0b83_z.jpg

You can use Gson to parse/deserialize to model class.
Or if you want to parse manually, then you have to parse a json object first and then you have to parse it again from a parsed json.
Eg.
JsonObject jsonObject = new JsonObject(jsonString);
JsonObject infoObject = jsonObject.getJsonObject("info");
String description = infoObject.getString("description");

updating json value of a nested json array in a json file | Java

I have this below json content in a file.
[
{
"prjId": 1,
"name" : "ABC",
"issueCounter": 7,
"issue": [
{
"id": 1,
"status" : "Closed",
"comment" : "blah blah blah",
"loggedBy": "shdkjdlsj"
},
{
"id": 2,
"status" : "Open",
"comment": "nothing",
"loggedBy": "xyz"
}
]
},
{
"prjId": 2,
"name" : "XYZ",
"issueCounter": 7,
"issue": [
{
"id": 3,
"status" : "Closed",
"comment": "jjjjjjjj",
"loggedBy": "klwm"
},
{
"id": 4,
"status" : "Closed",
"comment": "test test test",
"loggedBy": "NACK"
}
]
}]
I am able to parse this file and then traverse this json to get to the node where i wish to update. Upon reaching that point, i am confused on how to update it so that it would reflect on file on filesystem.
JSONParser parser = new JSONParser();
JSONArray rootArray = (JSONArray) parser.parse(new FileReader(pathToFile+fileName));
JSONObject project=null;
for (Object rootEntry : rootArray)
{
project = (JSONObject) rootEntry;
if( 1 == (Long) project.get("prjId"))
{
JSONArray issueArray = (JSONArray) project.get("issue");
for (Object issueEntry : issueArray)
{
JSONObject issue = (JSONObject) issueEntry;
System.out.println((Long) issue.get("id"));
if(2==(Long) issue.get("id"))
{
//now update the "comment" attribute here.
System.out.println("updated the comment: "+trckParam.getComment());
}
}
}
I have just the json reader till this point so do I construct a String as-and-when I traverse the nodes and when i reach the point I need to update, I update it (and construct the remainder of the nodes in this json object, (not to break from the loop)) and then write the entire reconstructed string to same file? Or is there a better approach where I can traverse the JSONObject and once i update it, push the entire object onto a file without constructing a String of entire file.
I still need to figure out a way to take either of the approach. So any pointers or direction will be greatly helpful.

How to access JSON data with multiple array objects : android

I am stuck in getting the data from the JSON file with multiple data sets.
{
"status": "ok",
"count": 3,
"count_total": 661,
"pages": 133,
"posts": [
{
"id": 20038,
"type": "post",
"slug": "xperia-launcher-download",
"url": "http:\/\/missingtricks.net\/xperia-launcher-download\/",
"status": "publish",
"title": "Download Xperia Launcher app for Android (Latest Version)"
},
{
"id": 94,
"type": "post",
"slug": "top-free-calling-apps-of-2014-year",
"url": "http:\/\/missingtricks.net\/top-free-calling-apps-of-2014-year\/",
"status": "publish",
"title": "Best Free Calling Apps for Android November 2014"
},
{
"id": 98,
"type": "post",
"slug": "top-free-calling-apps-of-2016-year",
"url": "http:\/\/missingtricks.net\/top-free-calling-apps-of-2016-year\/",
"status": "publish",
"title": "Best Free Calling Apps for Android December 2016"
}
]
}
I need to access the title, url and status from the above JSON file.
#Override
protected void onPostExecute(String result) {
//this method will be running on UI thread
pdLoading.dismiss();
List<DataFish> data = new ArrayList<>();
pdLoading.dismiss();
try {
JSONArray jArray = new JSONArray(result);
// Extract data from json and store into ArrayList as class objects
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
DataFish fishData = new DataFish();
fishData.status = json_data.getString("status");
fishData.title = json_data.getString("url");
fishData.sizeName = json_data.getString("title");
data.add(fishData);
}
} catch (JSONException e) {
Toast.makeText(JSonActivity.this, e.toString(), Toast.LENGTH_LONG).show();
Log.d("Json","Exception = "+e.toString());
}
}
I am getting a JSONException with the above code.
What should I do to access the title,status and url from the JSON File?

You have to fetch your JSONArray which is inside a JSONObject , so create a JSONObject and fetch your array with index "posts"
1.) result is a JSONObject so create a JSONObject
2.) Fetch your JSONArray with index value as "posts"
3.) Now simply traverse array objects by fetching it through index
JSONObject jObj = new JSONObject(result);
JSONArray jArray = jObj.getJSONArray("posts");
// Extract data from json and store into ArrayList as class objects
for (int i = 0; i < jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
DataFish fishData = new DataFish();
fishData.status = json_data.getString("status");
fishData.title = json_data.getString("url");
fishData.sizeName = json_data.getString("title");
data.add(fishData);
}
Note : i don't know weather it is a sample response with shorter version though your json object should ends with } not with , .
[{"id":20038,"type":"post","slug":"xperia-launcher-download","url":"http://missingtricks.net/xperia-launcher-download/","status":"publish","title":"Download
Xperia Launcher app for Android (Latest Version)",
// ^^^ there should be a } not a , to end json
// so make sure to do the correction so it will look like => ...st Version)"},
{"id":94,"type":"post","slug":"top-free-calling-apps-of-2014-year","url":"http://missingtricks.net/top-free-calling-apps-of-2014-year/","status":"publish","title":"Best
Free Calling Apps for Android November 2014", ]
Improvements :
you can use optString to avoid null or non-string value if there is no mapping key
This has two variations
Get an optional string associated with a key. It returns the
defaultValue if there is no such key.
public String optString(String key, String defaultValue) {
fishData.status = json_data.optString("status","N/A");
// will return "N/A" if no key found
or To get empty string if no key found then simply use
fishData.status = json_data.optString("status");
// will return "" if no key found where "" is an empty string

You can validate your JSON here.
If entire JSON getJsonObject() is not working, then you should parse JSON objects & array in multiple arrays then use them.

json array to individual strings

Assignment: I am using json-simple. How can I convert this json data into individual java strings?
(Please forgive me if you think that this is a low-level question - I am new to JSON, so I don't know much about that - I've searched a lot, but I couldn't find any answers)
I can get the data if there is only one object ... like this ...
{
"name": "Abhi",
"age": "21"
}
But, I can't get the data if it is in the array
[{
"name": "Abhi",
"age": "21"
}, {
"name": "shek",
"age": "7"
}]
my program logic for json object
JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader("A:/c/dataFile.json"));
JSONObject jObj = (JSONObject) obj;
String gName = (String) jObj.get("name");
String gAge = (String) jObj.get("age");
System.out.println(gName);
System.out.println(gAge);
Can anyone show me how to get the data? maybe a code snippet?
Thanks in advance for your answer!

Because in your second case you are getting JSONArray
you may need to check the instance of obj as
if (jObj instanceof JSONObject)
else if (jObj instanceof JSONArray)

read json file and parse inner json array in java

{
"vers": 0.01,
"config": {
"rate": "perhr",
"valueColumns": [
"vCPU",
"ECU",
"memoryGiB",
"storageGB",
"linux"
],
"currencies": [
"USD"
],
"regions": [
{
"region": "us-east",
"instanceTypes": [
{
"type": "generalCurrentGen",
"sizes": [
{
"size": "t2.micro",
"vCPU": "1",
"ECU": "variable",
"memoryGiB": "1",
"storageGB": "ebsonly",
"valueColumns": [
{
"name": "linux",
"prices": {
"USD": "0.013"
}
}
]
},
{
"size": "t2.small",
"vCPU": "1",
"ECU": "variable",
"memoryGiB": "2",
"storageGB": "ebsonly",
"valueColumns": [
{
"name": "linux",
"prices": {
"USD": "0.026"
}
}
]
}
]
}
]
}
]
}
}
Hi, i wanted to read this json file. I tried various ways from google but getting a null at valuesColumns. I have to read sizes array and have to put in list.

I think it will help your cause if you format your json. As it is it's quite hard to read. Googling for a JSON beautifier quickly found me this one.
When working with JSON your browser console provides a nice environment for inspecting and playing with the data. I pasted it into the browser console and did (hit enter after each line):
var x = { ... paste JSON here ... }
x
x.config
x.config.valueColumns
This tells me that x is a JSON object, config is a JSON object and valueColumns is a JSON array
Now to java. Grab yourself a json library, and accessing valueColumns will be something like:
JSONObject x = new JSONObject("{ ... JSON string ... }");
JSONObject config = x.getJSONObject("config");
JSONArray valueColumns = config.getJSONArray("valueColumns");
You can then iterate over valueColumns and pull out what you need.
Note that the above only gets you to the first valueColumns array under config. By following the same principle you can go deeper into the structure and get out the valueColumns for the objects in the sizes array if that's what you're really after.

For parsing json to java there are simple step.
Below code snippet may help you.
// parse json to java
Object obj = parser.parse(s);
JSONObject json = (JSONObject) obj;
JSONObject o = (JSONObject) json.get("config");
//get json array.
JSONArray array = (JSONArray) o.get("valueColumns");
System.out.println(array.toJSONString());
//access element by index
System.out.println(array.get(0));